Floating dry docks



docked on the rest thereof.

States Patent Christopher J. Foster, 44 Whitehall St.-, Sands Point,N.Y.

Filed Mar. 14, 1957, Ser. No. 645,937

7 Claims. (Cl. 114-46) My invention relates to an improvement infloating drydocks and has for its object to provide a self-dockingfloating drydock of great economy of structure. The invention relatesespecially to the Rennie type of floating drydock having continuoussteel wings spanning a series of detachable pontoons, one ofwhich mayreadily be It is established by the prior art that the introduction of acentral air space or buoyancy chamber into-adry- 'dock' having arectangular pontoon body is an expensive luxury, as the bulkheadstherefor and bracing of the chamber materially add to the weight of thedock center. Ordinarily, in a pontoon of rectangular crosssection havingsuch a chamber, no benefitby way of reducing the size or strength of theparts can be obtained-v by decreasing the transverse stressesencountered, at the time the wings are first pumpedout; because thetransverse bending moments-with the" ship raised, control the design ofthe conventional dock, and the-addition of a heavy central buoyancychamber will materially increaseflthe transverse bending moments withthe ship raised. Now, however, I have discovered that in a Rennie typeof dock, where the continuous steel wingsare provided with heavycontinuous bottoms, the weight of the wings, wing seats and fasteningsoppose the ship momentto such a degree that the combined transversestresses at the timethe wings are first pumped out with the pontoonsstill full ice The ensuing parallelogrammic section of the pontooninsures a substantial freeboard at the center of the pontoon while itcuts the bilge water left in the pontoon into half of that of theconventional dock. Due to the combination of square pontoon ends, whichlie at the sides of the completed dock, lower than the center of thedock with a center buoyancy chamber, and the required wing Width as wellas the dock-width substantially reduced, my preferred self dockingfloating drydock weighs only 25% of its lifting capacity, which is aneconomy of structure never before achieved. As my invention comprises anew combination of old elements from which new and useful results flow,-I do not claim only the combination of continuous sidewalls anddetachable parallelogrammic pontoons with center buoyancy chambers as myinvention, but I also claim as a method the several steps necessary toachieve said novel and useful results. In the. drawing- Fig. I isa'longitudinal elevation showing the center pontoon docked ontheremaining two pontoons. Fig.

I 10,- divides each pontoon into two pumping compartments are thecontrolling factors; and I have also discovered that theouse of.a-central buoyancy chamber, within'rectangular pontoons further reducesthe controlling stresses in such a dock when the wings are first pumpedout. This efiectis produced in two wayszi-The additional buoyancy causesthe dock tofioat higher. and thereby reducesthe water pressure on theoutside of the dock, and the" buoyancy chamber provides asubstantial'cen tral lift instead of having a central ship Jloadsupported controlling factors in the conventional Rennie'dock withrectangular pontoons are thecombined transverse stresses when thezwingsare first pumped out, a considerable economy of structure isachieved bythe introduction of a center'buoyancy chamber in ,this'type'of-dockFurther, the detachableppontoon is rendered laterallystable by thebuoyancy chamber, and noheavy longitudinal bulk-, heads arerequired forlateral stability ,in'my preferredpontoon, which alsofor-;allipracticakpiurposes is renderedunsinkable when separated fromthe dock. In my ponor chambers 17, which chambers communicate with theWingcompartments 19, through the communication openings 21,-. that arecut through the wing bottoms 14. A deck 5 near the tops of each wingvpartitions oifa safety hold 20, the buoyancy of which will prevent anaccidental sinking of the dock. The center pontoon 3, in Fig. I is showndocked when raised on special blocking7, while the ship8 shown in Fig.II is docked when raised on the regular blocking 9. For longitudinalstability of the dock,u the continuous wings, which I, foreconomyreasons prefer tomake rectangular in cross section are part-itionedoif by bulkheads 6, that end at the safety deck 5. i Thepontoons are shown fastened to the continuous wings by the bolts 15, andthe two pumping compartments of the pontoon are divided at their bottomby shallow swash bulkheads 11, that are provided with the swing checkvalves 12, which open only towards the sides 3 of the dock and closetowards the central chamber 18; sothat if the dock should careen orheel, the flow of water from the high side of thedock through thebulkhead on that SideltOWflTds thelow side of-the dock is prevented;this 'is-refiected in a considerable saving in the wing thickness,without a reduction in the stabilityof the loaded self docking, and thebuoyancy chamber is provided with called to the fact that .the outsidewater line 16 is subt'o'on construction-ifor very, wide dock-,-;,whereswash bulkheads: are 'required ito prevent a suddenof; waterjust whenthe ship has been lifted-clear out :of the; water andthe" metaceutric'height ofLship and dock is suddenly reduced to 'a; minimum,. I-' preferto iinstalli a shallow Serial No. 633383, permitting :thewater to drain.;towards;

swash bulkhead," just high enoughtowutor top the inside water planewhile. the ship bottom-. is still, sub; 7

' merged; This 1 shallow swash bulkhead "is supplied-with checkvalves'such shown in my copending application 70.

dock. 1 a a 7 Figures II and III indicate that the width of the .buoy- TV Y ancy chamber does not exceedone-fifthof the entirethepumps that arelocatedat'the sides: ofthe ..docls',- 1 width oflthe doclg and that;each pumping chamber 17 stantially, higher than the ship bottom when theshipin the dock is still substantially submerged s'o that thestabilizingeffect of'the ships waterplane is still in effect when thepartial' swash"bulkhead 11 cuts the free waterline 16 in halfithusadding to the'stability of the dock and ship, 'when' they pass throughthe critical zone,

wherethe water planes of the-wings alone stabilize' the beside thebuoyancy chamber is twice as large, having twice the width of thecentral chamber. Hence the lifting capacity of the dock is four timesits weight, and the weight of the dock, due to the buoyancy of thechain-j ber 18, is only 25% of the lifting capacity thereof.-

It is to be noted that portions 22 of the bottom of the chambers 17slope downward from the central chamber 18 towards the sides of thedock, beneath the wings 2; and portions of the deck 23 slope downwardfrom the central chamber 18 towards the wings; and these slopingportions 23 of the deck are substantially parallel to the slopingportions 22 of the bottom. Hence, when the dock has been sunk and theship is in place between the wings, and the dock is pumped out so thatthe ship rises, and the level of the water in the chambers 17 sinkstowards portions 22 of the bottom, the water in the chambers 17 tends toflow downward and sideways towards the spaces under the walls, andconcentrate in such spaces. The advantage of the buoyancy chamber istherefore greatest, and the Water in the chambers 17 is largest involume and heaviest adjacent the sides under the walls 2, and has a verymarked balancing efiect on the dock and the load of the ship; andimmensely increases the stability of the dock as the ship is liftedentirely out of the water and the deck of the dock is entirely above thelevel thereof.

Figures II and III indicate that the shortest dimension of each pontoonextends along the sides of the dock when the pontoon is in position, andthe longest dimension extends transversely of the clock. I prefer tocall the longest dimensions of the pontoons the sides thereof, becausethe pontoons are disposed side by side when assembled; and the shorterdimensions may therefore be regarded as the ends of each pontoon;although these ends extend along the sides of the completed dock. Fromthis it follows that the buoyancy of the central dock forming pumpingchambers, said walls being in communication with said pumping chambersat the ends of each pontoon, the central chamber being such size thatthe buoyancy effect thereof is greater than the submerged weight of thepontoon but smaller than the submerged weight of the pontoon and theportions of the wings super-imposed thereon, the bottom of each pontoonslop ing downward from the sides of the central chamber towards the endsof the pontoon under the wing walls thereon and being lowest directlyunder said wing walls.

3. In a self-docking floating dry dock, a row of pontoons arranged sideby side longitudinally of the dock,

' continuous wing walls supported on the ends of said chamber is largerthan the submerged weight of the 1011- t toon, but smaller than thecombined weight of the pontoon and the weight of the wing portionssuperposed thereon; that is, the central buoyancy chamber will supportthe pontoon afloat even when it is filled with Water, but the dock willsink when the pontoon and wings are both filled. r I do not wish to beunderstood to limit my claims. to the shown structure as it is evidentthat alterations and modifications may be made in the adaptation of myinvention without departing from the scope and spirit thereof. r

I claim: x v 1. In a self-docking floating dry dock, a row of pontoonsarranged side by side longitudinally of the dock, continuous wing wallssupported on the ends of said pontoons, said endsbeing directly undersaid walls, detachable means for securing the pontoons to the walls,each pontoon having a relatively shallow central buoyancy chamber, thespaces between the said buoyancy chamber pontoons, said ends beingdirectly under said walls, detachable means for securing the pontoons tothe walls, each pontoon having a central buoyancy chamber, the spacesbetween the said buoyancy chamber and the ends of said pontoons at thesides of the dock forming pumping chambers, said walls being incommunication with said pumping chambers at the ends of each pontoon,the central chamber being such size that the buoyancy effect thereofisi'greater than the submerged weight of the pontoon but smaller thanthe submerged weight of the pontoon and the portions of-the wingssuper-imposed thereon, the bottom of each pontoon sloping downward fromthe sides of the central chamber towards the ends of the pontoon underthe wing walls thereon and being lowest directly under said walls, saidbuoyancy cham' bers having swash bulkheads extending longitudinally ofthe dock along the sloping bottom, each bulkhead having one-way valvestherein which open only towards the side of the dock.

4. A self-docking dry dock comprising hollow wing walls and a row ofseparated hollow pontoons substantially rectangularin cross-sectionarranged side by side longitudinally of said dock, the ends of saidpontoons been directly under said wing walls, each pontoon 'having acentral buoyancy chamber and spaces forming pumping chambers between thebuoyancy chamber and saidwalls, said pumping chambers being incommunication with the interior of said walls, the bottom of saidpumping chambers sloping downward towards the sides walls and a row ofseparated hollow pontoons substanand the ends of said pontoons at thesides of the dock forming pumping chambers, said walls being incommunication with said pumping chambers at the ends of each pontoon,the central chamber being such size that the buoyancy eifect thereof isgreater than the sub merged weight of, the pontoon but smaller than thesubmerged weight of the pontoon and the portions of the wingssuperimposed thereon, the dock having a deck a pontoon having arelatively: shallow central buoyancy chamber, the=spaces between thesaid buoyancy cham-,

her and the ends, ofzsaidpontoons 'at the sides .of :the'

tially rectangular in cross-section arranged side by side longitudinallyof said dock, the ends of said pontoons be ing directly under said sidewalls, each pontoon having a central buoyancy chamber and spaces formingpumping chambers between the buoyancy chamber and said walls,saidpumping chambers being in communication with'the interior of saidwalls, the bottom of said pumping chambers sloping downward towards thesides of t the dock, and being lowest under said walls, saidpumppumpingchambers sloping downward towardsthe sides,

ing chambers having swash bulkheads on said sloping bottoms extendinglongitudinally of said dock, the width of said buoyancy chamber beingsubstantially one-fifth of the width of saidtdock, each bulkhead havingone-way valves therein which open only towards the side-of thedock.-' 1.7 Y

6. A-self-docking dry dock comprising hollow wing walls and a row ofseparated hollow pontoons substantially rectangular in cross-sectionarranged side by side longitudinally of said dock, the ends of saidpontoons being directly under said side walls, each pontoon having acentral-buoyancy chamber and spaces forming pumping chambers between thebuoyancychamber and said walls, saidpumping chambers being inCOlIllTlllIIlQfi tion with the interior of saidwalls, the-bottom of;said ofthe'idock, andnbeingilowest'under said walls, said;

ans 52mph, 4

pumping chambers having swash bulkheads on said sloping bottomsextending longitudinally of said dock, each' bulkhead having one-Wayvalves therein which open only towards the side of the dock, the widthof said buoyancy chamber being substantially one-fifth of the width ofsaid dock, and the pumping chambers extending over the remainder of theWidth of the dock, so that the lifting capacity of the dock is greatlyincreased.

7. In a self-docking floating dry dock, a row of pontoons arranged sideby side longitudinally of the dock, continuous wing Walls supported onthe ends of said pontoons, said ends being directly under said Walls,detachable means for securing the pontoons to the walls, each pontoonhaving a central buoyancy chamber, the spaces between said buoyancychamber and the ends of said pontoons at the sides of the dock formingpumping chamhers, low bulkheads in each pumping chamber extendinglongitudinally of the dock, each bulkhead having valves opening onlytowards the sides, the pontoons having substantially constant depth fromend to end, said Walls being in communication with said pumping chambersat the ends of each pontoon, the central chamber being of such size thatthe buoyancy efiect thereof is greater than the submerged Weight of thepontoon, but smaller than the submerged Weight of the pontoon and theportions of the Wings superimposed thereon.

: References Cited in the file of this patent UNITED STATES PATENTS

